1. Field of the Invention
The present invention relates to an inkjet recording apparatus, and more particularly to technology for effectively suppressing both cockling and stacker blocking while maintaining drying performance.
2. Description of the Related Art
In an inkjet recording method in which droplets of aqueous ink are deposited onto a sheet of recording medium, such as paper, cellulose fibers in the sheet swell and deform due to permeation of the water contained in the ink into the sheet, and a phenomenon (hereinafter referred to as “cockling”) occurs, in which the image formation area of the sheet becomes undulated. When cockling occurs, recording quality is degraded, and therefore cockling is a particularly serious problem when the ink deposition volume is large.
Furthermore, when performing double-side printing, ink droplets are deposited onto the rear surface of a sheet of recording medium in which cockling has occurred due to the ink deposition on the front surface, and therefore the sheet may come into contact with the ink ejection head, which gives rise to an even greater problem.
In order to suppress cockling, it is necessary to dry the recording surface swiftly after the ink deposition, in order to suppress the permeation of the water contained in the ink into the sheet of recording medium, as much as possible. For example, Japanese Patent Application Publication No. 2008-179012 discloses promoting drying of printed surfaces of a sheet of recording medium through heating a recording surface and a rear surface, by hot air flow drying of the printed surface of the sheet while heating and conveying the sheet with the rear surface of the sheet in tight contact with a drum contact surface adjusted to a prescribed temperature.
However, if drying of the recording surface is promoted, the temperature of the recording surface becomes excessively high in the output section after drying and a phenomenon (hereinafter referred to as “stacker blocking”) occurs due to the sheets of recording medium sticking together when the sheets are stacked up in the output tray or stacker.
In this way, if drying of the recording surface is promoted in order to suppress cockling, stacker blocking occurs, whereas if the promotion of drying of the recording surface is restricted in order to avoid the occurrence of stacker blocking, then cockling occurs. Furthermore, even if the drying of the recording surface is not adequate due to insufficient drying, stacker blocking still occurs and therefore it is necessary to maintain drying performance.
In the drying unit of inkjet recording apparatus in the related art, it is not currently possible to suppress the occurrence of both cockling and stacker blocking, while maintaining drying performance.